Well it’s not dahdi per se, it is dahdi’s signalling over ISDN PRI’s (Q931) of which a reference:-
So, colloquially
http://networking.ringofsaturn.com/Routers/isdncausecodes.php
look for cause 41, which basically means that although you have a connection to your PRI provider, they can’t route that call currently, the only recourse is with said “Provider”, They will almost certainly disagree with you but from the asterisk CLI
pri set debug on span 1
should give them something to chew on. If you want to get “intense” , then
pri set debug intense span 1
more to chew on.
Good Luck, you might need it 